1. Field of the Invention
This invention relates to a manufacturing method and a mold for a golf ball.
2. Description of the Related Art
Conventionally, as a manufacturing method for vulcanization molding of a layer of a core of a multi-piece solid golf ball or an one-piece ball or a solid center of a wound-string golf ball, Japanese Patent Publication No. 3-16244 (proposed by the applicant of the present invention) is known. This is a manufacturing method as shown in FIG. 7 and FIG. 8, of which purpose is improving working efficiency of takeout from the mold, in which a partial mold 40 has four grooves 41 in radius direction on a mating face 40a and ends of spews 42 generated in vulcanization molding are connected and unified one another. And, as another method, a manufacturing method with a partial mold which has no grooves on a mating face is widely used.
However, in the above manufacturing method in which the partial mold 40 has four grooves 41, enough charge of material is required. And, much amount of material of connected portion (spews) has to be wasted. Because the purpose of the above conventional manufacturing method is working efficiency in takeout of the molded product from the mold.
On the other hand, in the manufacturing method in which the partial mold does not have grooves, enough charge is required not to generate defects such as bare because material (rubber) spews out of some portions and becomes bare with little charge. And, an extra process of low temperature is required before main vulcanization to resolve remaining stress generated by the much charge and fulfill sphericity after the vulcanization molding. That is to say, cycle time is extended and productivity is reduced thereby.
It is therefore an object of the present invention to provide a manufacturing method and a mold for golf ball with which charge is little (without generating defection such as bare). And, it is another object of the present invention to provide a manufacturing method and a mold for golf ball with which a golf ball having good sphericity is made only with the main vulcanization (namely, with short cycle time).